How do I know if a request to my Apex controller originated from an XHR request or not?

Question

I have a Visualforce page that is backed by a controller. The page will make XHR requests back to the controller upon a number of events by making use of apex:actionSupport eg <apex:actionSupport event="onchange" action="{!UpdateWhatId}" reRender="inf_whatId,inf_location"/>.

I need the ability to distinguish between these XHR requests, and the initial page renders from within my controller.

How can I do this?

Answer 1

I guess you could add this to the part of your page where the method is called again:

<apex:actionSupport event="onchange" action="{!UpdateWhatId}" reRender="inf_whatId,if_location">
   <apex:param name="myFlag" value="true" assignTo="{!myBooleanValue}"/>
</apex:actionSupport>

Then in your class:

public boolean myBooleanValue {get;set;}

public void UpdateWhatId(){
    If(myBooleanValue){
       //do stuff when called from within page
    }else{
       //do stuff from action of vf pageload
    }

    myBooleanValue = false; //reset
}

Basically using the param tag you can set the value of a property in your class and tell if it came from where you wanted it or if the method was executed as part of the page load.

You could also have them call a different entry point:

add to class

public void fromPage(){
   myBooleanValue = true;
   updatewhatid();
}

Or on load you set the value of myBoolean to true when the method is executed and then you know it was ran. Subsequent calls to the method knows that it should enter the fromPage part instead of the on load part

public void UpdateWhatId(){
    If(myBooleanValue){
       //do stuff from action of vf pageload
    }else{
       //do stuff when called from within page
    }

    myBooleanValue = true; //Set to true to indicate it was ran the first time
}

It all depends on where this question goes after you have implemented the logic check

Answer 2

The environment doesn't tell you directly. However, you could build a private function and up to two public functions (depending on how the initial calling happens). Like so:

void doAction(Boolean first) {
    if(first) {...

public void doAction() {
    doAction(false);
}

Alternatively, depending on your use case, you could also just set a variable after the first time the function is called:

Boolean first = true;
public void doAction() {
    if(first) {
        ...
    }
    first = false;
}